The invention relates generally to electrical equipment. More particularly, the invention relates to a status detection apparatus for determining operating status of electrical equipment in real time through measurement of various parameters of fluid surrounding components of the electrical equipment, and to electrical equipment incorporating the status detection apparatus.
Electrical equipment, particularly medium-voltage or high-voltage electrical distribution equipment, require a high degree of electrical and thermal insulation between components thereof. Accordingly, it is well known to encapsulate components of electrical equipment, such as coils of a transformer, in a containment vessel and to fill the containment vessel with a fluid. The fluid facilitates dissipation of heat generated by the components and can be circulated through a heat exchanger to efficiently lower the operating temperature of the components. The fluid also serves as electrical insulation between components or to supplement other forms of insulation disposed around the components, such as cellulose paper or other insulating materials. Any fluid having the desired electrical and thermal properties can be used. Typically, electrical equipment is filled with an oil, such as castor oil or mineral oil, or a synthetic xe2x80x9coilxe2x80x9d such as chlorinated diphenyl, silicone oil, vegetable oil, or sulfur hexafluoride.
Often electrical distribution equipment is used in a mission critical environment in which failure can be very expensive or even catastrophic because of a loss of electric power to critical systems. Also, failure of electrical distribution equipment ordinarily results in a great deal of damage to the equipment itself and surrounding equipment thus requiring replacement of expensive equipment. Further, such failure can cause injury to personnel due electric shock, fire, or explosion. Therefore, it is desirable to monitor the status of electrical equipment to predict potential failure of the equipment through detection of incipient faults and to take remedial action through repair, replacement, or adjustment of operating conditions of the equipment.
A known method of monitoring the status of fluid-filled electrical equipment is to monitor various parameters of the fluid. For example, the temperature of the fluid and the total combustible gas (TCG) in the fluid is known to be indicative of the operating state of fluid-filled electrical equipment. Therefore, monitoring these parameters of the fluid can provide an indication of any incipient faults in the equipment. For example, it has been found that carbon monoxide and carbon dioxide increase in concentration with thermal aging and degradation of cellulosic insulation in electrical equipment. Hydrogen and various hydrocarbons (and derivatives thereof such as acetylene and ethylene) increase in concentration due to hot spots caused by circulating currents and dielectric breakdown such as corona and arcing. Concentrations of oxygen and nitrogen indicate the quality of the gas pressurizing system employed in large equipment, such as transformers. Accordingly xe2x80x9cdissolved gas analysisxe2x80x9d (DGA) has become a well accepted method of discerning incipient faults in fluid-filled electric equipment.
In known DGA methods, an amount of fluid is removed from the containment vessel of the equipment through a drain valve. The removed fluid is then subjected to testing for dissolved gas in a lab or by equipment in the field. This method of testing is referred to herein as xe2x80x9coff-linexe2x80x9d DGA. Since the gases are generated by various known faults, such as degradation of insulation material or other portions of electric components in the equipment, turn-to-turn shorts in coils, overloading, loose connections, or the like, various diagnostic theories have been developed for correlating the quantities of various gases in fluid with particular faults in electrical equipment in which the fluid is contained.
However, since known methods of off-line DGA require removal of fluid from the electric equipment, known methods do not, 1) yield localized position information relating to any fault in the equipment, 2) account for spatial variations of gases in the equipment, and 3) provide real time data relating to faults. If analysis is conducted off site, results may not be obtained for several hours. Incipient faults may develop into failure of the equipment over such a period of time. MICROMONITORS, INC(trademark) and SYPROTEC(trademark) have each developed a gas sensor which resides in the drain valve, or other single locations, of a transformer and overcomes some of the limitations of off-line DGA. However, location data relating to a fault is not discernable with such a device because it is located in one predefined position and does not provide any indication of the position of the source of the gas, i.e., the fault.
Various multiparameter sensors are known for detecting parameters such as temperature, acidity, concentrations of various gases, degree of polymerization or the like. For example, U.S. Pat. No. 5,591,321 discloses an array of semiconductor diode sensors, each for detecting a particular parameter. Also, distributed arrays of sensors have been used in various applications for detecting a single parameter, such as temperature. U.S. Pat. Nos. 5,191,206, 5,696,863, and 5,499,313 are exemplary of distributed temperature sensors. U.S. Pat. No. 4,827,487 discloses a distributed temperature sensor for electric motor stator windings. Distributed multiparameter sensing has been used in process control as exemplified by U.S. Pat. No. 5,586,305. U.S. Pat. No. 4,654,806 discloses an apparatus for monitoring transformers including a top oil temperature sensor and a hot spot temperature sensor located in a known hot spot of the transformer. However, this apparatus falls short of providing data required to localize faults.
Known processes and apparatus do not provide accurate, real-time data indicating the type and location of incipient faults in fluid filled electrical equipment. Also, since known processes do not account for spatial variations of parameters in fluid filled electric equipment, the accuracy of fault determinations with known processes is reduced.
The invention is directed toward a status detection apparatus, for electrical equipment comprising a plurality of distributed multiparameter sensors in a containment vessel or other fluid filled region of the electrical equipment. The sensors are capable of providing data relating to plural parameters of the fluid simultaneously at different positions in the fluid filled region. The data provided by the sensors can be processed to permit localization of incipient faults when combined with known flow data of the fluid through the electrical equipment.
A first aspect of the invention is an electrical apparatus, comprising a containment vessel configured to contain a fluid, at least one electrical component disposed in the containment vessel, and distributed multiparameter sensors disposed in the containment vessel. A second aspect of the invention is a status detection apparatus for detecting faults in electrical equipment of the type having a containment vessel configured to contain a fluid, and at least one electrical component disposed in the containment vessel. The status detection apparatus comprises distributed multiparameter sensors disposed in the containment vessel and configured to generate data indicative of sensed parameters, a data acquisition device for determining operating status of the electrical equipment, and means for conducting signals from the multiparameter sensors to the data acquisition device. A third aspect of the invention is an electrical transformer comprising a containment vessel, a transformer core having coils thereon, and distributed multiparameter sensors disposed in the containment vessel. A fourth aspect of the invention is a method of detecting operating status in electrical equipment of the type having a containment vessel, at least one electrical component in the containment vessel, and a fluid in the containment vessel surrounding the at least one electrical component. The method comprises the steps of sensing plural parameters of the fluid at plural sensing locations in the fluid simultaneously and determining operating status of the electrical equipment based on the results of the sensing step.